Switching from Windows Server to NAS

Switching from Windows Server to NAS

so I recently started my new job as an IT specialist in a small media
agency (~6-8 people). We currently struggle with the server crashing
occasionally (within 4h - 48h) probably due to a hdd / hardware raid
fault. Since we have a relatively large image database (~6TB), network- as
well as data-reliability has a high priority.
I am currently thinking about switching to two NAS (w/ raid5/6) since I do
not really see the need of an actual server with Windows Server 2008
having ~12TB disk space in RAID 6. We have a Seagate Blackarmor 400 NAS
with 4x2TB in RAID 5. This NAS also has 2x1 Gbit/s network connectivity,
which would perfectly fit the requirements.
With these specs, I do not see the need of a "regular" Windows server but
I am not sure about the NAS performance or the temperature getting too
high in case of high access.
I would be glad to hear any suggestion about this.
Thanks!